In prior art machines which harvest the power of fluids in motion it is common practice to employ a rotor upon which are affixed, milled or moulded variously formed blades, buckets, paddles, vanes or other such appendages so pitched thereupon that when subjected to a fluid current, continuous molecular impingements, foiling and eddying interactions between the fluid-mass supplied and the commonly pitched appendages results in rotation of the rotor to which they are attached. It is appreciable, however, that while appendages responsible for developing rotation may be designed to render minimized flow obstruction and may advantageously induce airfoil (or hydrofoil) speed beneficiation, a sizeable component of the working fluid's kinetic energy is nevertheless rendered unavailable for work conversion by such machines due to losses owing to: the shock of fluid impingement upon appendages exposed to the moving fluid streams, and the resultant re direction and eddying of fluid molecules resulting from the process of driving certain prior art rotors at 90° to the applied fluid currents for at least part of their cycle; the ‘swirl’ effect caused by fluid discharging tangentially and in some cases radially from bladed or annular rotors due to surface adhesion and centrifugal forces acting over the rotating blade profile contributing to the development of wasteful down-stream vortices; all components working to produce a disadvantageous backpressure effect tending to resist the forward momentum of subsequent fluid flow though the same cross-section. Attempts to reduce these effects have been made in some prior art such as by varying appendage pitch or yaw relationships with respect to some reference plane at key positions. with varying success, however, to compensate for the disadvantageous backpressure like effect, underutilization of swept areas is practiced by design, as evidenced by fluid-energy in a given cross-sectional area being allowed to pass through the area scribed out by the prior art appendages which occupy a limited percentage of the swept area 10 minimize the so-called Betz effect, defining the limiting efficiency of machines extracting energy from fluid currents in motion.
Run-of-river (ROR) hydro-electricity production is a less preferable form of energy extraction associated with river in-stream energy conversion (RISEC) which incurs varied ecological impacts depending upon specific method” employed. Unfortunately and typically, this involves the diversion of significant water resources into pen-stocks bound for points of generation some distance away, which invites ecological concern due to its considerable effect upon the habitat of aquatic life, a consequence that true RISEC applications may avoid.
While prior art in the emerging field of tidal in-stream energy conversion (TISEC) harvests clean energy from seawater in motion, these typically bladed devices present danger of injury to aquatic life which may be driven under powerful tidal or oceanic currents unto impact with rotating blades disposing moving obstacles in the path of indigenous aquatic creatures. Whereas skirt augmenters (5) may be employed to develop venturi-like pressure reduction behind bladed rotors housed within the skirts to increase rotor speeds and extractable power output with the generation of greater flow-rates there-through, these devices may concurrently increase the risk of more serious injury to aquatic life through the speed increases sought, especially at the blade extremities.
Thrupp type turbines (6) wherein working fluid shears across the surfaces of discs, both entering and exiting disc packs at substantially opposite points on disc peripheries, may be said to operate primarily in friction mode. Whereas this type of disc turbine has been erroneously been mistaken as representative of Tesla type disc turbines, it has been analyzed (21) and was calculated to operate comparatively at only 42% of the effectiveness of Tesla type turbines (22).
TISEC prior art provided by Belinsky (8) proposes utilization of funnel collectors with larger ends facing on-coming ocean currents and directing smaller concentrated flows accumulated by the funnels toward Darricus type turbines. Whereas collectors in the method provide added energy to turbines for conversion, these types of turbines suffer losses similar to those already described in respect to bladed turbines, and no means is provided for discharging into lower than ambient pressure fluid streams to increase the efficiency of the method.
The advantages disclosed by Finney (9) for use in various fluids including air and water further providing dramatic velocity and power increases in working mediums at length applied to axial turbines located adjacent the throat of serially staged venturis of sequentially larger cross-sections are significant, however, are also subject to energy losses described through their utilization of bladed turbines.
While Bosley (11) offers inherently minimized electrical generation losses leading to less heat loading of waters surrounding TISEC devices, even with the optionally proposed flow-enhancing shroud, the annular rotor comprising a plurality of paddles introduces bladed art deficiencies already discussed, and no impeller improvements are suggested to improve rotor speeds for greater conversion gains.
Borgesen (12) provides complete swept area utilizations in TISEC apparatus utilizing regularly spaced underwater sails gainfully driving transmission lines with the direction of the applied tidal force which further drive electrical power generation means. However, the drag coefficient utilized while limiting to cavitation permits significant energy escape in the fluid reintroduced to the ambient tidal flow resulting in lateral displacement thereof in a common direction potentially changing the sedimentation patterns at depth further affecting marine life habitats.
While Dial (13) provides overhung, fixedly spaced disc turbines having at least one adjustable inlet to vary the angle at which fluid contacts the discs, vary the rotational speed of the impeller, and further vary the volume of fluid flowing through the impeller assembly, means are not discussed for the utilization of natural fluid currents other than those induced to fall through a penstock, a device which the presently disclosed invention seeks to eliminate.
The wind-turbine of Stanton (14) suggests form-induced air acceleration with a funnel shaped concentrator and axial bladed turbine to harvest energy from the added pressure differential obtained via discharge of energized turbine throughput into a lower pressure region in the lee of the proposed collector, however, Stanton's method is also subject to the disadvantages described regarding bladed turbine losses, and similarly does not expound upon an advantageous method to further reduce downstream discharge back-pressures. Also, this method neither suggests nor enables service in non-compressible fluid environments as the 5% outlet to inlet cross-section disclosed would tend to stagnate the bulk of the fluid mass in water applications.
Whereas Couture (15) provides multiple sail collectors to concentrate combined wind feeds to supply a turbine for power generation means, the method disclosed requires that fluids provided by sail collectors undergo two energy consuming changes in direction prior to transfer through a lengthy conduit to work generation means, further reducing the work potential realized in the method through pipe friction losses within the conduit.
Bladed horizontal axis wind turbines and arrays thereof, generally thought to comprise modern-day wind-farms typically provide increased power benefit through installation in high wind areas, however, these areas may be coincident with fly-zones and/or nesting grounds of eagles, falcons and other endangered bird species put at risk of injurious collision with the moving rotors of such machines. Technologically assuming great proportion in part to overcome anticipated, previously described losses observed, bladed prior art spinning faster in high ground areas put birds of flight at increased risk of consequence. Further, the aesthetics of visual and sonic impacts in residential and other areas currently limit the extent to which wind energy harvest as it is known today is utilized.
Airborne prior art (16) comprising buoyant, inflatable rotors secured to ground stations via tethering may attain lofty station at altitude providing access to wind resources unsurpassed in the prior art. While offering large fluid collection surface areas and low ambient work generation fluid cut-in speeds, and rotors utilizing the Magnus effect for positional stability, they may otherwise adversely present obstacles for aviators, the power extraction capacity offered therein are nevertheless lower than bladed wind turbines.
Vertical-axis wind turbine art disclosed by Nica (17) employ Tesla disc turbine runners fitted with curved blades affixed about disc perimeters and helical ribs on disc surfaces, all centrally mounted for rotation within an array of stationary, tangentially arranged, outer fluid guiding members. While affording speed beneficiation of approaching wind via the convergent-divergent external guiding means disclosed, the disposition of internal disc-separating helical surface appendages provided may otherwise limit the efficiency of the disc turbine internally employed, since to provide best effect, working fluid in disc turbines should be free to travel in natural streamlines of least resistance (1) to maintain laminar flow between co-rotating discs. Whereas this may require that working fluid complete possibly many revolutions between disc surfaces for optimal effect, this requirement is largely prevented in the method by the inter-disc ribs forcing working fluid to follow multiple pre-designated trajectories each potentially introducing turbulence between discs and efficiency losses accordingly.
In general, issues such as low frequency noise from rotating blades slicing through gaseous and liquid fluids, cavitation of liquid fluids into gaseous fluid inclusions disrupting laminar flows across work generation surfaces further affecting both noise levels and power outputs alike in underwater turbines, and the general lack of machines able to engage greater fluid cross sections in work generation and or conversion currently limits the timely maximization of energy returns from machines of the prior art. Therefore there is a need for new method and systems for extracting power from moving fluids which may overcome more than one of these deficiencies in the prior art.
This background information is provided to reveal information believed by the applicant to be of possible relevance to the present invention. No admission is necessarily intended, nor should be construed, that any of the preceding information constitutes prior art against the present invention.